But in places like Tanzania, the challenges are unimaginable: discrimination, segregation, and even death. Local superstitions and traditions provoke attacks on people with albinism, whose limbs are used in witchcraft practices.

The public health and safety crisis for people with albinism in Tanzania has worsened in recent years, officials say. At least eight attacks were reported there between August 2014 and March 2015, according to the United Nations, with victims including a 1-year-old who was brutally killed and a 6-year-old whose hand was chopped off with a machete.

“These attacks are often stunningly vicious, with children, in particular, being targeted,” Zeid Ra’ad Al Hussein, the then-United Nations high commissioner for human rights, said last year.

Photographer Patrick Gries first learned of this sad situation in 2010, after his family moved to Tanzania for his wife's post-doctoral research. A newspaper ran a story about a farmer who was attacked by a mob of people who cut off both of his arms and ran away as he bled. "The farmer's body parts were meant to be sold for witchcraft with this belief that albino body parts and limbs would bring luck," Gries said.

"I had never heard about such a thing," he said. "It was constantly in my mind. I tried to understand, but there is nothing to understand. It goes way beyond what we can imagine."

Gries began photographing the lives of the people with albinism he met and pored over research about the condition. The things he learned painted a dire picture. In addition to the threat of violence, people with albinism in Tanzania face a life of segregation and poverty. Many are denied basic rights — in life and death.

"These persons, for the most part, do not have any official civil status or legitimacy," he said. "They have not been registered at birth. Similarly, they do not die, rather, they 'vanish.' There are no graves of albinos in cemeteries — people would come and steal the bones."

A lack of education and resources can lead to an increased risk of death from skin cancer and other conditions. Gries experienced that firsthand, when his friend and assistant Mathew Mlolwa, a Tanzanian man with albinism, died of cancer early this year. He has dedicated his photo series, In/Visibility, to Mlolwa.

Ahead, his powerful photos and stories. For more on how you can help, visit Under The Same Sun, an advocacy organization that helped connect Gries with some of his photo subjects.

Editor's note: This story has been updated to reflect Refinery29's style guide on describing people with albinism.